a8n: Add Comby campaign as example to docs

Created by: mrnugget

This is a campaign that I came up with with @unknwon. I think it's a great example to have because it showcases how to run Comby and then goimports on the resulting Go code.

It's not that easy to get the escaping in the JSON file to correctly pass things to Comby, so an example should help with that :)